Recently, various mixer devices are being developed which mix fluids in a laminar flow state in a flow channel having a width of a micro-scale and allow the fluids to diffuse through the contact interface. Such mixer devices are called a micro-mixer or a micro-reactor, and are developed for chemical reaction, micro-analysis, and the like applications. In conventional batch systems, mass production is conducted by enlargement, so-called scale-up, of the reaction vessel. In contrast, in production of a chemical substance or the like with the mixer device, the mass production can be attained by employing many mixer units arranged in parallel.
The above-mentioned mixer devices are in a size of micro-scale: the size of the flow channel is small, and the flow rate of the fluid in the flow channel is low, resulting in a small Reynolds number of the flow. Therefore, the fluid flowing through the flow channel in a micro-scale is generally laminar-flow-controlled, being different from the turbulent-flow-controlled batch type of reaction apparatus. Under the laminar-flow-controlled conditions, two fluids brought into contact are mixed mainly by diffusion through the interface of the two fluids. Further, in a micro-scale space in which the surface area for a unit volume is large, the diffusion mixing occurs quickly at the interface of the two laminar flows advantageously.
Generally, according to Fick's law, the time for diffusion is proportional to the square of the diffusion distance. Therefore, the time for the mixing by molecular diffusion is shorter for a smaller width of the flow channel. For the flow channel width reduced by a factor or 1/10, the mixing time is reduced by a factor of 1/100. In the micro-scale space, molecular transport, reaction, and separation proceed quickly by spontaneous behavior of the molecules without mechanical agitation.
Therefore, the reaction under the laminar flow conditions in a micro-scale reactor, the reaction can proceed at a higher rate than the reaction under turbulent conditions in a conventional batch type of reaction apparatus. In the laminar flow state, two liquids are brought into contact invariably at the same timing to be mixed or to react, enabling uniform mixing and regular reaction.
In a conventional batch type reactor, a primary reaction product can react further in the reactor to result in non-uniformity of the product. In particular, in production of a fine particulate material, particles formed primarily can react further to grow to cause non-uniformity of the fine particles. In contrast, in the micro-scale mixer device, the fluids flow through the micro-scale flow channel continuously without stagnation, which prevents a successive reaction of the formed fine particles to improve the uniformity of the formed fine particles.
Among various newly developed mixer devices, Japanese Patent Application Laid-Open No. 2003-210959, for example, discloses a mixer device for mixing effectively two fluids in a laminar flow state in a micro-scale flow channel. In the disclosed mixer device, two kinds of solutions are allowed to flow out through nozzles in slender bar-shaped laminar flows. The slender bar-shaped laminar flows have a large specific interface area of contact to enable shortening of the time for mixing.
However, the fluids introduced through adjacent nozzles will join together on leaving the nozzle into the mixing flow path. Therefore, it is not easy to form slender bar-shaped laminar flows. When the opening width is kept unchanged and the rod-shaped straightening member is made thick, a larger space could be occupied by the rod-shaped straightening member.
Japanese Patent Application Laid-Open No. 2001-340753 discloses a micro-reactor which allows plural chemical reactions to proceed by flowing plural kinds of fluids in one mixing flow channel. However, since the plural reactions proceed in one and the same mixing flow path, a fluid can remain partly in the flow channel to become an impurity in another chemical reaction.
The present invention is made on such a technical background, and intends to provide a fluid-processing device which utilizes a large specific interface area between the fluids to be mixed for effective diffusion without causing stagnation of the fluids and formed product in the micro-flow channel.